Are the contributors listed somewhere? If they are it is still up to the POTUS to honor them or shank them. He is POTUS, and POTUS can do what he wants. He can literally rat those people out, and tell the public what those contributors "want" the next POTUS to do.

He can make up some sinister conspiracy, and the public will demand something be done. He can then have those people arrested, and throw away key. Or he can be hush hush about any world domination schemes, and just play along.

I think campaign contributions absolutely dictate policy. How else do you think big business like big oil, big pharma, and big agriculture persuade government to hand them out subsidies, monopolies, tax breaks, etc? Government in a representative democracy is just a tool for special interest groups to do what they want irrespective of any will of the majority.

Complicated question and way beyond my ability to answer satisfactorily. Donations come in many forms at many levels for many reasons with many results. There are disappointed donors and winks & handshakes at all levels of politics. But there is for sure a perception among the American people that big money plays far too big a role in policy.

They're related, but you can't really buy access directly. Usually it's more of a case of spending money on people who you know and trust (or for big national spenders, guys who fit clear guidelines who you may vet in person) to support your interests.